Most frequently, a reefing slider device for a parafoil type parachute consists of a reinforced fabric panel, square or rectangular in shape, having a grommet or ring in each corner to allow passage of the suspension lines from each corresponding quadrant of the parachute canopy. Essentially, sliders, and the orifices through which the suspension lines pass, act as temporary constrictors around the suspension lines to delay the spreading action of the parachute. During the packing process, the slider is typically positioned as high as practical on the suspension lines, against the lower portion of the parachute canopy. During the opening process, the slider lower surface is initially exposed to high velocity airflow, which tends to keep the slider pushed up against the parachute lower surface. However, the high velocity air that is pushing the slider upward is also causing the parachute canopy to spread and inflate. At this phase of the opening process, the upper portions of the suspension lines emerge from the slider orifices at high angles and produce strong mechanical force for pushing the slider downward. The aerodynamic upward force must resist the very strong force that is pushing the slider downward and the slider effectiveness is extremely dependent on the relationship between these two forces during this very dynamic, and somewhat chaotic, period. The somewhat random outcome of the conflict between these two opposing forces determines in large part, why slider reefing works very effectively in some instances and much less effectively in others.
A great majority of the complaints regarding slider reefing are due to highly dynamic parachute opening forces, which result from the slider reefing time period being randomly insufficient for properly controlling the parachute opening event.
The lack of precision in slider reefing control makes their use problematic for a wide range of load/altitude/speed applications. Due to imprecise control of the parachute opening process, a slider reefed parachute opening that is very acceptable at relatively low altitude and relatively low airspeed may injure a parachutist and/or damage the parachute at higher altitudes or higher speeds. The same phenomenon holds true for non-human payloads. Under some opening conditions, the payload may be damaged or the parachute may suffer structural failure due to insufficient opening control being provided by the reefing slider.
To combat the higher than desirable forces that result from using the basic reefing slider configuration, various slider modifications have been devised in attempts to increase the reefing time interval provided by the sliders for overcoming the effects of other than optimal circumstances. In general terms, the modifications have consisted of adding fabric, in the form of drag producing flags, or modifying the slider shape to cause it to act more like a parachute.
Because reefing slider devices, including the modified slider designs, do not provide precise opening control, Reuter developed a much more sophisticated reefing means for parafoil type parachutes which is taught in U.S. Pat. No. 4, 846,423. This reefing means has been quite successful for aerospace applications, which often demand very precise reefing control due to their extreme operating environments.
The Reuter reefing system, while quite precise and predictable in its performance, is quite labor intensive and time consuming to prepare for use. Furthermore, it requires expendable pyrotechnic cutting devices which are quite costly and present some safety concerns when they are being installed and used. The features that make this system precise and predictable also cause it to be impractical for widespread usage.
It appears that the designers of the prior art modified reefing slider configurations did not recognize that the same sort of chaotic airflow patterns that plague conventional sliders would also plague their modified slider configurations. Because the performance characteristics of the previous modified reefing slider devices are also totally dependent on the erratic aerodynamic forces that occur at the time of parachute deployment and opening, no modified slider configuration has demonstrated precise and predictable performance over a wide performance range. Therefore, the lack of precision in slider reefing control continues to make their use problematic for a wide range of load/altitude/speed applications.
It is therefore an object of the invention to provide a performance improvement to a parachute reefing slider means.
It is another object of the invention to provide a performance improvement that is significantly less dependent on aerodynamic forces than are prior art reefing slider means.
It is another object of the invention to improve the performance of the parachute reefing slider means by incorporating a regulated friction producing slider descent retardation means.
It is another object of the invention to improve the reefing slider means by providing the friction producing means consisting of a cord which passes through a restriction means.
It is another object of the invention to produce an improved reefing slider means with reduced fabric flutter, therefore, reduced noise.